Detection of anti-Histoplasma capsulatum antibodies and seroconversion patterns in critically ill patients with COVID-19: An underdiagnosed fungal entity complicating COVID-19?

The patients with severe COVID-19 are at increased risk for invasive fungal infections, such as invasive pulmonary aspergillosis and candidiasis, which increase morbidity and mortality. However, clinicians should also consider the possibility of reactivating latent Histoplasma capsulatum in patients with severe COVID-19 living within areas of endemicity who have worsening respiratory function or sepsis, even if they do not have classical risk factors for histoplasmosis (e.g., HIV/AIDS). Bearing in mind this scenario, serum samples of 39 non-HIV/AIDS patients from Buenos Aires hospitalized due to severe COVID-19 pneumonia were analyzed for anti-H. capsulatum-specific IgG antibodies by an in-house ELISA. Antibodies against H. capsulatum were detected in the sera of 8/39 patients (20.51%). To exclude the possibility that these antibodies arose from past exposure of these patients to the fungus, paired serum samples obtained after an interval of at least 10 days were evaluated. Of them, five patients (62.5%) with negative anti-H. capsulatum antibodies at baseline became seropositive 7-10 days later. Three patients (37.5%) had positive anti-H. capsulatum antibodies at baseline, but at time point 2, one of them became seronegative and the other one diminished the antibody titers (4000 vs. 16000 at baseline). The remaining patients displayed higher antibody titers at time point 2 (4000 vs. 1000 at baseline) and died immediately thereafter. In conclusion, awareness of the possibility of fungal co-infections is essential to reduce delays in diagnosis and treatment in order to help prevent severe illness and death from these infections. LAY SUMMARY: This study verifies that patients with severe COVID-19 at ICU are at risk for histoplasmosis reactivation in endemic areas. Accurate diagnosis of this deadly fungal disease among critically ill patients with COVID-19 living in endemic areas for histoplasmosis is needed.

Epidemiology and outcomes of allergic bronchopulmonary aspergillosis in the elderly.

BACKGROUND: The prevalence and outcomes of allergic bronchopulmonary aspergillosis (ABPA) in the elderly remain unknown. METHODS: We reviewed our database to identify the proportion of subjects diagnosed with ABPA at ≥60 years of age (ABPA-elderly). We compared the clinical features, treatment and outcomes of ABPA-elderly versus the non-elderly (ABPA diagnosed at <60 years of age). RESULTS: Between 2007 and 2019, we encountered 810 ABPA subjects with a mean age of 34.9 years (49.4% women). Of these, 43 (5.3%) were aged ≥60 years (ABPA-elderly). There was a trend towards lower median (interquartile range [IQR]) serum total IgE (4900 [2659-10000] vs. 7156 [23360-11963] IU/mL; P = .06) and Aspergillus fumigatus-specific IgE (12.3 [4.8-29.6] vs. 22.4 [7.7-41.5] kUA/L; P = .06) in the elderly than the non-elderly. Eosinophil counts were similar in the two groups. The median [IQR] number of segments involved by bronchiectasis (5 [2-9] vs. 7 [4-11]) was significantly lower in the ABPA-elderly (P = .001). The proportion of subjects experiencing ABPA exacerbations was significantly (P = .047) lower in the elderly (25.6%) vs. the non-elderly (40.8%). There was also a tendency towards a lower mean number of exacerbations in the elderly (155 vs. 208 exacerbation per 1000 person-years) than the non-elderly (P = .09). There was also a trend towards longer mean time to first exacerbation in the ABPA-elderly than the non-elderly (1612 vs. 1159 days). CONCLUSION: ABPA was uncommon in the elderly. The bronchiectasis is less extensive with a trend towards lower immunological severity and fewer exacerbations in the elderly than the non-elderly subjects with ABPA.

COVID-19-associated subacute invasive pulmonary aspergillosis.

BACKGROUND: Though invasive pulmonary aspergillosis is a well known complication of COVID-19 pneumonia, indolent forms of aspergillosis have been rarely described. METHODS: We prospectively collected the clinico-radio-microbiological data of 10 patients of subacute invasive pulmonary aspergillosis (SAIA), who presented to our hospital with recent history of COVID-19 pneumonia along with cavitary lung disease, positive IgG (against Aspergillus) with or without positive respiratory samples for Aspergillus spp. RESULT: The mean age of presentation of SAIA was 50.7 ± 11.8 years. All the patients had recently recovered from severe COVID-19 illness with a mean duration of 29.2 ± 12 days from COVID-19 positivity. Cough was the predominant symptom seen in 8/10 (80%) patients followed by haemoptysis. 7/10 (70%) patients were known diabetic. While serum galactomannan was positive in 5/9 patients (55.5%), fungal culture was positive in 2/7 patients (28.5%) and polymerase chain reaction (PCR) for Aspergillus was positive in three patients. Eight (80%) patients presented with a single cavitary lesion; pseudoaneurysm of pulmonary artery was seen in two patients and post-COVID-19 changes were seen in all patients. All patients were treated with voriconazole, out of which four (40%) patients died during the follow-up period. CONCLUSION: SAIA should be considered in the differential diagnosis of cavitating lung lesions in patients with recent history of COVID-19 in the background of steroid use with or without pre-existing diabetes.

Biomarkers for the diagnosis of invasive candidiasis in immunocompetent and immunocompromised patients.

Blood culture methods show low sensitivity, so reliable non-culture diagnostic tests are needed to help clinicians with the introduction, de-escalation, and discontinuation of antifungal therapy in patients with suspected invasive candidiasis (IC). We evaluated different biomarkers for the diagnosis of IC in immunocompetent and immunocompromised patients at risk for developing invasive fungal diseases. The specificity of Candida albicans germ-tube antibodies (CAGTA) detection was high (89%-100%), but sensitivity did not exceed 61% even after raising the cut-off from 1/160 to 1/80. We developed enzyme-linked immunoassays detecting antibodies against C. albicans proteins (Als3-N, Hwp1-N, or Met6) that resulted more sensitive (66%-92%) but less specific than CAGTA assay. The combination of 1,3-beta-D-glucan (BDG) detection and CAGTA results provided the highest diagnostic usefulness in immunocompetent patients. However, in immunocompromised patients, anti-Met6 antibodies was the best biomarker, both, alone or in combination with BDG.

Identification of Disease-Associated Cryptococcal Proteins Reactive With Serum IgG From Cryptococcal Meningitis Patients.

Cryptococcus neoformans, an opportunistic fungal pathogen ubiquitously present in the environment, causes cryptococcal meningitis (CM) mainly in immunocompromised patients, such as AIDS patients. We aimed to identify disease-associated cryptococcal protein antigens targeted by the human humoral immune response. Therefore, we used sera from Colombian CM patients, with or without HIV infection, and from healthy individuals living in the same region. Serological analysis revealed increased titers of anti-cryptococcal IgG in HIV-negative CM patients, but not HIV-positive CM patients, compared to healthy controls. In contrast, titers of anti-cryptococcal IgM were not affected by CM. Furthermore, we detected pre-existing IgG and IgM antibodies even in sera from healthy individuals. The observed induction of anti-cryptococcal IgG but not IgM during CM was supported by analysis of sera from C. neoformans-infected mice. Stronger increase in IgG was found in wild type mice with high lung fungal burden compared to IL-4Rα-deficient mice showing low lung fungal burden. To identify the proteins targeted by human anti-cryptococcal IgG antibodies, we applied a quantitative 2D immunoproteome approach identifying cryptococcal protein spots preferentially recognized by sera from CM patients or healthy individuals followed by mass spectrometry analysis. Twenty-three cryptococcal proteins were recombinantly expressed and confirmed to be immunoreactive with human sera. Fourteen of them were newly described as immunoreactive proteins. Twelve proteins were classified as disease-associated antigens, based on significantly stronger immunoreactivity with sera from CM patients compared to healthy individuals. The proteins identified in our screen significantly expand the pool of cryptococcal proteins with potential for (i) development of novel anti-cryptococcal agents based on implications in cryptococcal virulence or survival, or (ii) development of an anti-cryptococcal vaccine, as several candidates lack homology to human proteins and are localized extracellularly. Furthermore, this study defines pre-existing anti-cryptococcal immunoreactivity in healthy individuals at a molecular level, identifying target antigens recognized by sera from healthy control persons.

Immunization with Pneumocystis carinii A121-85 antigen activates immune function against P. carinii.

BACKGROUND: Pneumocystis pneumonia (PcP), which is caused by Pneumocystis carinii, is a life-threatening infection that affects immunocompromised individuals. Unfortunately, chemoprophylaxis and dapsone are only effective for half of the patients with PcP, indicating that additional preventive methods are needed. We predicated the pneumocystis surface protein A12 sequence 1-85 by DNAStar software and BepiPred, and identified it as a potential vaccine candidate by bioresearch. METHODS: We used recombinant A121-85 as antigen to immunized mice and detected serum titer of IgG, expression of inflammatory factors by EILSA, qRT-PCR and flow cytometry. RESULTS: Our results showed that immunization with recombinant A121-85 increased the serum titer of IgG, promoted the secretion of T lymphocytes, increased the expression of inflammatory factors, and elevated lung inflammatory injury in mice. CONCLUSIONS: Our findings suggest that A121-85 is a potential vaccine target for preventing Pneumocystis carinii. The evaluation of A121-85-elicited antibodies in the prevention of PcP in humans deserves further investigation.

Evaluation of an Aspergillus IgG/IgM lateral flow assay for serodiagnosis of fungal asthma in Uganda.

BACKGROUND: Diagnosis of fungal allergies in asthma remains problematic in low-and middle-income countries due to non-availability of point-of-care testing. In this study, we aimed to evaluate the performance of an Aspergillus immunochromatographic technology (ICT) IgG/M lateral flow device (LFD) for the serological diagnosis of allergic bronchopulmonary aspergillosis (ABPA) and severe asthma with fungal sensitisation (SAFS) among Ugandan adult asthmatics. METHODS: 374 adult (aged ≥18years) asthmatics in the African Severe Asthma Program study, Ugandan site constituted the study population. ABPA and SAFS were diagnosed according to standard criteria. Asthmatics who did not meet the above criteria constituted a control group. The LFD tests were performed and read according to manufacturer's instructions. RESULTS: ABPA was found in 12/374 (3.2%) and SAFS in 60/374 (16%) participants. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the Aspergillus ICT for the diagnosis of ABPA were 0.0%, 96.4%, 0.0% and 96.7% respectively, and for SAFS 6.7%, 97.1%, 30.8% and 84.5% respectively. False positive and negative rates were 3.5% and 3.2% for ABPA and 2.4% and 14.9% for SAFS, respectively. Patients with a positive LFD significantly had higher median Aspergillus fumigatus-specific IgE levels compared to those with negative LFD (median: 0.06 kUA/l VS 0.03 kUA/L, P = 0.011). CONCLUSION: The Aspergillus ICT IgG/M LFD had a poor diagnostic performance for the diagnosis of both ABPA and SAFS. Its greatest value may be in distinguishing chronic and allergic aspergillosis in Africa.

Fungal asthma among Ugandan adult asthmatics.

Fungal sensitization is associated with poor asthma control. We aimed to determine the prevalence and factors associated with fungal asthma among Ugandan adults. Individuals aged ≥18 years with a new diagnosis of asthma in the last 12 months participating in the African Severe Asthma Program constituted the study population. Skin prick test results, clinical and demographic data were retrieved from the database, and serum Aspergillus fumigatus specific antibodies and total IgE were measured in stored blood. We enrolled 374 patients, median (IQR) age 34 (25-45) years, 286 (76.5%) females and 286 (76.5%) with severe asthma. Prevalence of Aspergillus fumigatus sensitization was 42.0% (95% CI: 37.1-47.0%), allergic bronchopulmonary aspergillosis (ABPA) 3.2% (1.8-5.5%), severe asthma with fungal sensitization (SAFS) 16% (12.7-20.1%) and allergic bronchopulmonary mycosis (ABPM) 2.9% (1.7-5.2%). Older age (55-64 years) (crude odds ratio (cOR) = 2.6), sensitization to at least one allergen (cOR = 9.38) and hypertension (cOR = 1.99) were significantly associated with Aspergillus sensitization, whereas tertiary education level (cOR = 0.29), severe depression (cOR = 0.15) and strong emotions (cOR = 0.47) were not. High occupational exposure to Aspergillus (cOR = 4.26) and contact with moulds (cOR = 14.28) were significantly associated with ABPA. Palpitations (cOR = 5.54), uncontrolled asthma (cOR = 3.54), eczema/dermatitis (cOR = 3.07), poor lung function (cOR = 2.11) and frequent exacerbations (cOR = 1.01) were significantly associated with SAFS. Eczema/dermatitis (cOR = 1.55) was significantly associated with ABPM, but cold weather trigger (cOR = 0.24) was not. Fungal asthma is a significant problem among Ugandans with asthma and should be particularly considered in individuals who remain uncontrolled despite optimal standard of care for asthma, as it is responsive to available and affordable oral antifungal therapy. LAY SUMMARY: This study showed that fungal asthma is a significant problem among Ugandans with asthma with a high prevalence. Fungal asthma should be considered in patients with uncontrolled asthma despite receiving optimal standard of care. This is the first modern attempt to define these endotypes of asthma in Africa.

Peripheral immune profile of children with Talaromyces marneffei infections: a retrospective analysis of 21 cases.

BACKGROUND: Talaromyces marneffei (T. marneffei) is an opportunistic pathogen that infects immunodeficient children. The aim of the study is to determine the clinical features and peripheral immune state of Talaromyces marneffei (T. marneffei) infections in children for early detection and diagnosis. METHODS: We retrospectively reviewed 21 pediatric patients who were diagnosed with T. marneffei infections and were followed up in the Guangzhou Women and Children's Medical Center from January 2010 to January 2020. For each patient, we collected and analyzed clinical characteristics, peripheral immunological results, genetic tests, complications and prognosis. RESULTS: Common clinical features of the patients included fever (20/21, 95.24%), cough (17/21, 80.95%) and hepatomegaly (17/21, 80.95%). Severe complications included septic shock (12/21, 57.14%), hemophagocytic lymphohistiocytosis (HLH) (11/21, 52.38%), acute respiratory distress syndrome (ARDS) (10/21, 47.62%), multiple organ dysfunction syndrome (MODS) (9/21, 42.86%), and disseminated intravascular coagulation (DIC) (7/21, 33.33%). Eleven children (11/21, 52.38%) eventually died of T. marneffei infections. All patients were HIV negative. Seven cases revealed reduced antibody levels, especially IgG. Higher levels of IgE were detected in 9 cases with an obvious increase in two patients. Ten patients showed decreased complement C3 levels, some of whom had low C4 levels. Three patients displayed decreased absolute T lymphocyte counts, including the CD 4+ and CD 8+ subsets. A reduction in NK cells was present in most patients. No patient had positive nitro blue tetrazolium (NBT) test results. Nine patients were screened for common genetic mutations. Of the cases, one case had no disease-specific gene mutation. Four children had confirmed hyperimmunoglobulin M syndrome (HIGM) with CD40LG variation, one case had severe combined immunodeficiency (SCID), and one case had hyper-IgE syndrome (HIES). One patient was identified as having a heterozygous mutation in STAT3 gene; however, he showed no typical clinical manifestations of HIES at his age. One patient had a mutated COPA gene with uncertain pathogenic potential. Another patient was diagnosed with HIES that depended on her clinical features and the National Institutes of Health (NIH) scoring system. CONCLUSIONS: T. marneffei infections in HIV-negative children induced severe systemic complications and poor prognosis. Children with T. marneffei infections commonly exhibited abnormal immunoglobulin levels in peripheral blood, particularly decreased IgG or increased IgE levels, further suggesting possible underlying PIDs in these patients.

Effect of patient immunodeficiencies on the diagnostic performance of serological assays to detect Aspergillus-specific antibodies in chronic pulmonary aspergillosis.

BACKGROUND: Prevalence of chronic pulmonary aspergillosis (CPA) is ~3 million patients worldwide, and detection of Aspergillus-specific antibody is a critical diagnostic component. Some patients with CPA have subtle immune deficits possibly contributing to poor Aspergillus antibody production and false negative results. MATERIALS/METHODS: We analyzed patient data from 167 cases of clinically confirmed CPA previously evaluated by ImmunoCAP Aspergillus-specific IgG EIA, Bordier ELISA and LDBio Aspergillus IgG/IgM ICT lateral flow assay, to identify deficiencies in: mannose binding lectin (MBL), IgG, IgA, IgM, IFN gamma, IL12 or IL17 production, and/or low cell marker counts (CD4, CD19, CD56). We defined patients as 'sero-negative' if ImmunoCAP Aspergillus IgG was consistently and repeatedly negative (<40 mg A/L). 'Sero-positive' was defined as all other CPA cases. RESULTS: We found the rate of false negatives by ImmunoCAP Aspergillus IgG EIA (n = 23) to be more prevalent in patients with immunodeficiency markers, especially multiple defects. MBL deficiency combined with low CD19 cells (p < 0.001), pneumococcal antibody levels (p = 0.043), IgM (p = 0.047) or three combined (p = 0.001-0.018) or all four together (p = 0.018) were significant. The performance LDBio Aspergillus IgG/IgM ICT appears to be relatively unaffected by immunodeficiency (92.7% of ImmunoCap sero-negatives were positive). The Bordier assay performed significantly better than the ImmunoCAP assay (P = 0.0016) for sero-negative CPA cases. CONCLUSIONS: In select cases of CPA, ImmunoCAP EIA yields a false negative result, making serological diagnosis difficult. ImmunoCAP false negatives are more prevalent in patients with multiple immunological defects, who may still be positive with the LDBio Aspergillus ICT or Bordier EIA.

Interplay between Humoral and CLA+ T Cell Response against Candida albicans in Psoriasis.

Candida albicans (CA) infections have been associated with psoriasis onset or disease flares. However, the integrated immune response against this fungus is still poorly characterized in psoriasis. We studied specific immunoglobulins in plasma and the CA response in cocultures of circulating memory CD45RA- cutaneous lymphocyte antigen (CLA)+/- T cell with autologous epidermal cells from plaque and guttate psoriasis patients (cohort 1, n = 52), and also healthy individuals (n = 17). A complete proteomic profile was also evaluated in plaque psoriasis patients (cohort 2, n = 114) regarding their anti-CA IgA levels. Increased anti-CA IgA and IgG levels are present in the plasma from plaque but not guttate psoriasis compared to healthy controls. CA cellular response is confined to CLA+ T cells and is primarily Th17. The levels of anti-CA IgA are directly associated with CLA+ Th17 response in plaque psoriasis. Proteomic analysis revealed distinct profiles in psoriasis patients with high anti-CA IgA. C-C motif chemokine ligand 18, chitinase-3-like protein 1 and azurocidin were significantly elevated in the plasma from plaque psoriasis patients with high anti-CA levels and severe disease. Our results indicate a mechanism by which Candida albicans exposure can trigger a clinically relevant IL-17 response in psoriasis. Assessing anti-CA IgA levels may be useful in order to evaluate chronic psoriasis patients.

Chitosan hydrogel loaded with recombinant protein containing epitope C from HSP90 of Candida albicans induces protective immune responses against systemic candidiasis.

We reported previously a recombinant protein (rP-HSP90C) containing epitope C from heat shock protein 90 of Candida albicans mediates protective immune responses against systemic candidiasis. However, it exhibits weak immunogenicity. Therefore, we evaluated the potential and mechanisms of thermosensitive chitosan hydrogel (CH-HG) as an adjuvant in rP-HSP90C vaccine. CH-HG synthesized by ionic cross-linking showed buffering capacity and control-released rP-HSP90C in vitro. In comparison to naked rP-HSP90C, CH-HG-loaded rP-HSP90C (CH-HG/rP-HSP90C) not only evoked a long-lasting rP-HSP90C-specific IgG, but also enhanced Th1, Th2, Th17 responses and the ratio of Th1/Th2 in vivo; Meanwhile, CH-HG/rP-HSP90C provoked a stronger CTL response than rP-HSP90C. Notably, CH-HG increased the protective immune responses against systemic candidiasis in rP-HSP90C-immunized mice since CH-HG/rP-HSP90C enhanced the survival rate of infected mice, and diminished the CFUs in kidneys compared to rP-HSP90C, which were similar to that of QuilA. Further in vitro investigation displayed CH-HG upgraded the expressions of costimulators, MHCs and cytokines in BMDCs compared to rP-HSP90C；CH-HG also promoted cellular uptake, endosomal escape and "cross-presentation" of rP-HSP90C. In addition, it recruited immune cells at the injection site. Our study demonstrated that CH-HG can be an efficient adjuvant in fungal vaccines.

A quantitative enzyme-linked immunoassay (ELISA) to approximate complement-fixing antibody titers in serum from patients with coccidioidomycosis.

Coccidioidomycosis is most frequently diagnosed serologically, and the quantitative test for complement-fixing antibodies is considered prognostically useful. Because complement-fixing antibody testing is complex, labor-intensive, and poorly standardized, an enzyme-linked immunoassay (ELISA) alternative would be attractive. In this report, we restrict the complement-fixing, antibody-binding domain to a 200-amino-acid recombinant peptide of the known antigen. Over-lapping truncations of this peptide do not bind complement-fixing antibodies, suggesting that the responsible epitope(s) are conformational. Further, anchoring the antigenic peptide to the ELISA plate by means of a C-terminal biotin-mimic peptide tag instead of allowing the peptide to randomly adhere to the plastic plate improves sensitivity of antibody detection by 1-2 logs in different sera. The newly developed ELISA shows a significant quantitative correlation with complement-fixing antibody titers. This ELISA shows potential as the basis for a new quantitative assay for coccidioidal antibodies.

Seroepidemiological survey on sporotrichosis-infection in rural areas of the south of Minas Gerais State, Brazil.

Sporotrichosis is a subcutaneous mycosis caused by traumatic inoculation into the skin by fungi species of the genus Sporothrix. The disease has different clinical manifestations (cutaneous, lymphocutaneous, and disseminated), and can also progress to a systemic infection. Despite having a worldwide distribution, sporotrichosis is most prevalent in tropical and subtropical countries. In Brazil, reports of the disease are higher frequent, where cases of the disease were found in Rio de Janeiro, Sao Paulo, Curitiba, Pernambuco, and Paraiba, among others. Certain groups of people may be more exposed to the causative agent of disease, such as residents of rural areas. Thus, this work aimed to carry out a seroepidemiological survey of the prevalence of sporotrichosis in four rural locations in the south of Minas Gerais State, Brazil. In this study, we used an indirect ELISA test in the survey on the prevalence of sporotrichosis. Data obtained in this study evaluated a population of 631 individuals and showed a prevalence of 44.69%. The distribution of seroprevalence of sporotrichosis with respect to age groups and gender showed no significant statistical difference. Thus, we found a high seroprevalence of sporotrichosis-infection in rural regions of southern Minas Gerais State, Brazil, with no difference in prevalence in relation to gender and age.

IgG reactivity profile to Paracoccidioides spp. antigens in people with asymptomatic Paracoccidioidomycosis.

Introduction. Paracoccidioidomycosis (PCM) is a systemic mycosis caused by Paracoccidioides spp. As the disease is known to affect mostly men over 40 years old who previously worked handling soil, some cities of agricultural economy in endemic regions may have more cases of paracoccidioidal infection.Gap statement. The true frequency of PCM cannot be established in Brazil because it is not a disease of mandatory reporting. The detection of paracoccidioidal infection may assist in the planning of health services, in order to provide early detection of the disease and to prevent its worsening or even progression to death. In addition, little is described about sera reactivity with antigens from different species of Paracoccidiodes, especially P. lutzii.Aim. Current research was conducted in an inland municipality of southern Brazil, in order to assess infection rate within this endemic region of PCM disease.Methodology. ELISA was employed to evaluate 359 sera from random volunteers from Guarapuava, Paraná, Brazil, to detect IgG against cell-free antigens (CFA) from P. restrepiensis B339, P. americana LDR3 and P. lutzii LDR2. Confirmatory ELISA employed gp43 from B339. Reduction of cross-reactions was sought by treatment with sodium metaperiodate (SMP-CFA, SMP-gp43). Immunoblot was performed with 37 selected sera among those reactive in ELISA. Epidemiological profile was assessed by questionnaire.Results. ELISA reactivity was: CFA/SMP-CFA in general 37.3/17.8 %, B339 25.3/14.5 %, LDR3 24.5/1.4 %, LDR2 8.3/5.8 %; gp43/SMP-gp43 7.2/4.7 %. There were sera reactive with multiple CFAs. In immunoblot, five sera showed the same reaction profile with P. lutzii's antigens as PCM disease sera. Rural residence and soil-related professions were risk factors for paracoccidioidal infection.Conclusion. The low prevalence is in accordance with previous reports of lower PCM disease endemicity in Guarapuava than in other areas of Paraná. Although P. brasiliensis seems to be the prevalent strain of the region, 21 sera from people who only lived in Guarapuava reacted with P. lutzii LDR2. CFA-ELISA with whole antigens seems a good option for serological screening in epidemiological surveys.

An initial survey of 150 horses from Thailand for anti-Pythium insidiosum antibodies.

INTRODUCTION: Pythium insidiosum causes a life-threatening infection termed pythiosis in humans and other animals. The organism has been identified in tropical and subtropical environments worldwide. Since 1985, human pythiosis has been increasingly reported from Thailand. Seroprevalence studies estimated that 32,000 Thai people had been exposed to the pathogen. In 2018, the first animal pythiosis case in Thailand was diagnosed in a horse. Here, we investigated the seroprevalence of anti-P. insidiosum antibodies in the Thai equine population. MATERIALS AND METHODS: We surveyed serum anti-P. insidiosum antibodies in 150 horses distributed across Thailand, using three established serological tests: enzyme-linked immunosorbent assay (ELISA), immunochromatographic test (ICT), and Western blot analysis. RESULTS: ELISA detected the anti-P. insidiosum antibodies in three horses. ICT and Western blot confirmed the presence of the antibodies in one of the ELISA-positive horses. Based on one positive out of 150 horses tested, the seroprevalence of anti-P. insidiosum antibodies in the Thai equine population was 0.7%, which is markedly higher than that in the Thai human population (0.07%), but much lower than that in the Brazilian equine population (11.1%). CONCLUSION: The seroprevalence of the anti-P. insidiosum antibodies in the equine population suggests a higher incidence of pythiosis in horses than in humans. The antibody surveillance reported by our group was undertaken to promote a better understanding of the epidemiology and host susceptibility of pythiosis in Thailand.